1. Field of the Invention
The present invention relates to a printer with which a continuous-page sheet feeder is releasably engageable, and particularly to a printer which is capable of detecting a state of releasable engagement with the continuous-page sheet feeder.
2. Description of the Prior Art
In a printing apparatus, i.e., a printer with which a continuous-page, sheet feeder, e.g., a tractor feeder is releasably engageable, it is necessary to change the printing operation of the printer according to the state of releasable engagement with the tractor feeder. If the printing is made on a cut sheet without employing the tractor feeder, there is used a typewriter, a printer or the like wherein the sheet is fed together with the rotation of a platen in such a state that the sheet is brought into contact with the platen serving as a sheet feeder provided inside the printer. If the tractor feeder is mounted and the printing is made on a continuous-page sheet in the typewriter, the printer or the like referred to above, the sheet is released from being brought into contact with the platen and hence the sheet is fed only by the tractor feeder.
This is because there are instances when the sheet feeding direction of the platen and that of the tractor feeder are not necessarily coincident with each other. In such a situation, a slight deviation can take place between the platen and the tractor feeder, resulting in wrinkling of the sheet or in tightening or clogging of the sheet.
In a typewriter, a printer or the like wherein the printing is made while moving a carriage with a printing head placed thereon in a transverse direction with respect to the sheet feeding direction, any position of the carriage at the time of insertion of the sheet gives rise to a problem in the case where the printing is made on the cut sheet without employing the tractor feeder. This is attributable to the fact that there is no device to guide the cut sheet along the sheet feeding direction on the platen and the sheet is inclined on the platen when the carriage is brought into contact with the left or right margin of the sheet.
To this end, when the cut sheet is printed without mounting the tractor feeder, the cut sheet is controlled such that it does not incline even when the carriage is brought into contact with the cut sheet and the carriage is also so controlled that it is located in the center of the width of the printing sheet in advance upon insertion of the sheet.
In this way, in the printer with which the tractor feeder is releasably engageable, it is necessary to change the printing operation of the printer, depending upon whether the tractor feeder is mounted on the printer or it is released therefrom. Thus, in the conventional printer, a switch or the like is provided on the body side of the printer in order to detect the state of the releasable engagement with the tractor feeder. When the tractor feeder is mounted on the printer, the switch or the like is turned on thereby to detect the state of the releasable engagement with the tractor feeder on the printer body.
Such a detection method is technically similar to that for detecting the state of the releasable engagement with a cut sheet feeder, which is of a type disclosed, e.g., in U.S. Pat. No. 4,756,636.
However, if a detecting member such as a switch, etc. is provided in the printer in order to detect the state of the releasable engagement with the tractor feeder in the above-described manner, a problem will arise in that the number of components used for the printer is increased and the manufacturing cost is raised because of the provision of the detecting member, a control means or the like.